Method For Operating A Regenerative Heat Exchanger And Regenerative Heat Exchanger Having Improved Efficiency

ABSTRACT

A regenerative heat exchanger, including a rotor mounted so it is rotatable, which has at least one first gas volume flow to be heated and at least one second gas volume flow to be cooled flowing through it, as well as a method for operating the regenerative heat exchanger, is provided. The inflowing first gas volume flow enters the rotor at a first front side of the rotor and exits the rotor again at a second front side of the rotor at an outflowing first gas volume flow. To increase the heating performance, a leakage volume flow is captured at the first front side of the rotor and supplied to the inflowing first gas volume flow and/or a leakage volume flow is captured at the second front side of the rotor and supplied to the outflowing first gas volume flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to foreign Patent Application EP08021916.5, filed on Dec. 17, 2008, the disclosure of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a method for operating a regenerative heatexchanger, in particular for air preheating in power plants.Furthermore, the invention relates to a regenerative heat exchanger.

BACKGROUND OF THE INVENTION

Regenerative heat exchangers of the relevant type (also only referred toas heat exchangers hereafter) are used for heat transfer from at leastone gas volume flow to at least one other gas volume flow. For thispurpose, the heat exchanger can comprise a rotating (and/or alsorevolving) storage mass (referred to hereafter as a rotor), which movesrelative to fixed flow connections and is alternately heated by the atleast one gas volume flow and cooled down again by the at least oneother gas volume flow, whereby heat energy is transferable from at leastone gas volume flow to at least one other gas volume flow.

The rotor of a regenerative heat exchanger is typically implemented asan essentially circular-cylindrical drum, slight deviations from thisshape being possible. The rotor has a central rotational axis. The gasvolume flows flow through the rotor essentially parallel to therotational axis. The flow through is typically in opposite directions(so-called counter flow method). In order to provide sufficient heatstorage mass, but also increase the mechanical stability of the rotor,it is sectored or segmented into multiple cells or chambers, which arealso used as the flow channels for the gas volume flows. Heat-storagemasses are typically situated in these chambers, such as so-called heattransfer plate packs.

In operation, a warm and/or hot gas volume flow flows through theindividual chambers of the rotor, the gas being able to be flue gas froma combustion process, for example. Because the warm or hot gas volumeflow flows through, the heat-storing masses of the chambers which itflows through heat up. Heat is withdrawn from the gas volume flowflowing through, so that it has a lower temperature upon exiting therotor than upon entering. As a result of the rotor rotation, the heatedchambers finally reach the section where a cooler or cold gas volumeflow, such as fresh air, flows through the rotor and is heated on theheat-storing masses of these chambers, the heat-storing masses thencooling down again. With this type of heat transfer, a type of heatstorage capability of the rotor is used in order to heat a first gasvolume flow and cool a second gas volume flow.

Alternatively, a rotor can also be implemented as fixed, for example,and the flow connections may move relative thereto.

If the fresh air is used as the gas volume flow to be heated, the heatexchanger can be used for so-called air preheating. The efficiency of apower plant can be increased and the pollutant discharge can be reducedby air preheating.

To reduce mass losses and/or volume losses in regard to the gas volumeflows, a complex seal is required on the rotor, which has been thesubject of numerous refinements for some time. The sealing system for arotor typically comprises at least one peripheral seal and at least oneradial seal. A peripheral seal seals the gas volume flows flowingthrough the rotor at the external circumference of the rotor to theoutside. A peripheral seal can comprise an axial seal and/or lateralseal on the outer circumference of the rotor. A radial seal is toprevent a so-called flow short-circuit and/or short-circuit volume flowbetween the individual gas volume flows at a rotor front side. As aresult of the relative movement of the rotor to the seals and because ofchanging heat expansion, gaps and/or residual gaps between the seals andthe rotor are unavoidable, through which leakage volume flows occur, inparticular between the gas volume flows (so-called flow short-circuits),typically from the gas volume flow having the higher pressure to the gasvolume flow having the lower pressure. In addition to volume losses,this also results in energy losses and thus in unsatisfactoryefficiency.

Suction methods and suction facilities are known from the prior art forimproving the efficiency of regenerative heat exchangers, however, thesemethods and facilities typically do not result in improvements of theefficiency for the transfer of the heat energy in practice. Worsening ofthe efficiency has sometimes even been observed.

SUMMARY OF THE INVENTION

Embodiments of the present invention advantageously improve theefficiency of a regenerative heat exchanger.

In a method for operating a regenerative heat exchanger, according to anembodiment of the invention, the rotor, which is preferably mounted soit is rotatable, has at least one first gas volume flow to be heatedflowing through it, such as fresh air in particular, the gas volume flowheating on the heat-storing masses as it flows through the rotor. Thisis used in particular for air preheating of fresh air for a power plant.Furthermore, the rotor has at least one second gas volume flow to becooled flowing through it, such as flue gas and/or combustion gas orexhaust gas in particular, which dissipates its heat to the heat-storingmasses of the rotor and is itself cooled in this way.

The rotor has a first front side or front face, at which the inflowingfirst gas volume flow to be heated enters the rotor. The rotor has asecond front side or front face opposite to the first front side, atwhich the outflowing first gas volume flow to be heated exits the rotoragain. The first front side is typically also referred to as the “coldside” and the second front side as the “hot side”.

The first gas volume flow and the second gas volume flow are sealed onthe rotor using at least one rotor seal, in order to limit volume lossesand particularly flow short-circuits. A rotor seal is particularly aperipheral seal, which seals a gas volume flow on the outercircumference of the rotor, and/or a radial seal, which seals the gasvolume flows relative to one another and is to prevent flowshort-circuits and/or short-circuit volume flows.

Because leakage volume flows occur in the area of a rotor seal, it isprovided according to the invention that at least one leakage volumeflow is acquired and/or captured on the first front side, or in the areaof this front side, of the rotor and supplied to the inflowing first gasvolume flow, and/or at least one leakage volume flow is acquired and/orcaptured on the second front side, or in the area of this front side, ofthe rotor and supplied to the outflowing first gas volume flow.

A leakage volume flow is particularly a short-circuit volume flow fromthe first gas volume flow into the second gas volume flow, which occursin the area of a radial seal at the first front side of the rotor or atthe second front side of the rotor. Thus, strictly speaking, this is arecirculation of a captured leakage volume flow into the first gasvolume flow to be heated.

The acquisition or capture of a leakage volume flow, which occurs in thearea of a rotor seal, typically cannot be performed completely fortechnical reasons, so that acquisition or capture of a leakage volumeflow in the scope of this invention relates to a substantial part of theleakage volume flow, which can be acquired and/or captured under theparticular technical conditions. Acquisition and capture are to beunderstood broadly in the scope of this invention and include allmeasures which are capable of handling a leakage volume flow.

The method differs from the prior art at least in that a leakage volumeflow is only captured in the area of one of the front sides or bothfront sides of the rotor. It can thus be differentiated whichtemperature level a leakage volume flow has in each case. Furthermore,the method, according to an embodiment of the invention, also differsfrom the prior art in that, as a function of the temperature level ofthe leakage volume flow, a corresponding supply or recirculation isperformed into the inflowing first gas volume flow, which is still cool,or the outflowing first gas volume flow, which has already been heated(always on the same side of the rotor in regard to flow technology).Energetic advantages are thus achieved, which increase the efficiencyrelative to the prior art, as explained in greater detail hereafter.

For a regenerative heat exchanger which is used in a power plant forheat transfer from a hot flue gas volume flow (from a combustionprocess) to a fresh air volume flow, for example, there is typically aleakage volume flow (short-circuit volume flow) from the fresh airvolume flow into the flue gas volume flow in the area of a radial seal.When determining the operating parameters and designing the regenerativeheat exchanger, such leakage volume flows are taken into consideration,because the leakage volume flow from the fresh air volume flow into theflue gas volume flow results in additional cooling of the flue gasvolume flow by approximately 3° to 7° K. (so-called “corrected” flue gasor exhaust gas temperature). There is thus a danger that the temperaturewill fall below the acid dewpoint temperature of a component of the fluegas to be cooled and damage (in particular corrosion) of followingfacility components (such as dust removal facilities and filterfacilities) in the flue gas train will occur. It must therefore beensured that the temperature of the flue gas volume flow at the exit ofthe rotor and/or upon exiting the regenerative heat exchanger, in spiteof the additional cooling by the leakage volume flow from the fresh airvolume flow, is higher than a critical acid dewpoint temperature. Theadditional cooling of the flue gas volume flow by the leakage volumeflow from the fresh air volume flow must therefore be taken intoconsideration in the design of the regenerative heat exchanger and itsoperating parameters. On the other hand, this additional cooling of theflue gas volume flow is not energetically available for the heattransfer from the flue gas volume flow to the fresh air volume flow.Accordingly, a lower “uncorrected” flue gas temperature is desirable.

Through the separate acquisition of a warm or hot leakage volume flowand the supply or recirculation thereof into the outflowing and alreadyheated fresh air volume flow, and/or a cool or cold leakage volume flowand the supply or recirculation thereof into the inflowing and (still)cool fresh air volume flow, the negative additional cooling effect canbe largely avoided. In other words: the now essentially “uncorrected”flue gas temperature can be lowered to a similar level as the earlier“corrected” exhaust gas temperature. With unchanged entry temperature ofthe gas volume flows into the rotor and with unchanged gas volume flows,as a result, the heat transfer from the flue gas volume flow to thefresh air volume flow can be increased, without the temperature fallingbelow a critical acid dewpoint temperature in the flue gas volume flow.The increase of the heat transfer is possible through constructivedesign of the heat-storing masses, for example.

As a result of the defined recirculation, undesired cooling of the fluegas volume flow before the rotor and also undesired cooling of the fluegas volume flow after the rotor are also largely avoided, whichadditionally increases the efficiency of the regenerative heatexchanger.

As a result, the outflow-side temperature (i.e., the temperature afterthe rotor and/or after the regenerative heat exchanger) of the fresh airvolume flow and thus the quantity of heat in the combustion air for thepower plant combustion process are increased. This additional quantityof heat reduces the fuel demand. In relation to a boiler performance of700 to 800 MW, savings in operating costs in the amount of ε150,000 toε400,000 per year may be reckoned without reduction of the power, thesavings increasing still further in the coming years because of risingfuel prices. A reduction of the discharge of pollutant gases, such asCO₂ in particular, results as a further substantial advantage.

According to an embodiment of the invention, it is preferably providedthat at least one leakage volume flow is captured on the first frontside of the rotor and supplied to the inflowing first gas volume flowand, to be precise, introduced or fed therein there, and at least oneleakage volume flow is captured on the second front side of the rotorand supplied to the outflowing first gas volume flow, and, to beprecise, introduced or fed therein there. Through this acquisition onboth sides (in relation to the front sides of the rotor) and separatesupply or recirculation of leakage volume flows, the efficiency of theregenerative heat exchanger improves significantly. Notwithstandingthis, of course, acquisition and supply or recirculation at only onefront side of the rotor is also possible and advantageous.

According to an advantageous refinement of the method, it is providedthat the supply or recirculation of the leakage volume flow capturedfrom the first front side of the rotor into the first gas volume flow isnot performed directly, but rather upstream from the rotor. “Upstream”means that the supply occurs before the rotor in the flow direction.Alternatively or additionally, it is provided that the recirculation ofthe leakage volume flow captured from the second front side of the rotorinto the first gas volume flow is not performed directly, but ratherdownstream from the rotor. “Downstream” means that the supply occursafter the rotor in the flow direction. The acquisition or capture of aleakage volume flow and its supply or recirculation into the first gasvolume flow are thus separated in design and construction.

It is provided in particular for this purpose that the supply orrecirculation of a captured leakage volume flow in the first gas volumeflow occurs in spatial proximity, preferably in direct proximity to therotor. The flow distances may thus be kept short in construction. Asupplied or recirculated leakage volume flow is only subject to a slighttemperature influence.

It is advantageously provided that at least one leakage volume flowacquired or captured at the first front side of the rotor and at leastone leakage volume flow acquired or captured at the second front side ofthe rotor are recirculated on separate paths in each case upstream intothe inflowing first gas volume flow and downstream into the outflowingfirst gas going flow. A path or recirculation path is any unit which iscapable of transporting or conducting a gas volume flow. A path orrecirculation path is particularly a line system made of pipes and pipesections or the like.

It is preferably provided for this purpose that at least one fan unit isused per path. A partial vacuum can be generated using the fan unit,using which a leakage volume flow can be acquired or captured at a frontside of the rotor by suctioning. An overpressure can also be generatedusing the fan unit, using which the suction leakage volume flow can besupplied or recirculated along the path or recirculation path to thefirst gas volume flow and introduced or fed therein. A fan unit isparticularly a ventilator, which is preferably situated in a linesystem.

Furthermore, it is preferable that at least one leakage volume flow isacquired or captured, preferably using suctioning, at the first frontside and/or the second front side of the rotor in the area of a radialseal. This measure thus relates to a particularly disadvantageousshort-circuit volume flow, in particular from the first gas volume flowinto the second gas volume flow.

It is also additionally or alternatively preferable that at least oneleakage volume flow is acquired or captured, preferably by suctioning,at the first front side and/or the second front side of the rotor in thearea of a peripheral seal. This also results in improvement of theefficiency.

According to a particularly preferred refinement of the inventivemethod, it is provided that at least one first gas volume flow to beheated and at least one second gas volume flow to be cooled flow throughthe rotor in opposite directions, i.e., in the counter flow method. Bothgas volume flows have a lower temperature level at the first front side(“cold side”) than at the second front side (“hot side”). It is thuseasy to differentiate which temperature level an acquired or capturedleakage volume flow has. A leakage volume flow acquired at the hot frontside of the rotor is supplied to the outflowing first gas volume flow orrecirculated therein and a leakage volume flow acquired at the coldfront side of the rotor is supplied to the inflowing first gas volumeflow or recirculated therein. Alternatively, the rotor can also have atleast two gas volume flows flowing through it in the same direction.

In a preferred refinement of the method, at least two first gas volumeflows are provided, at least one captured leakage volume flow,preferably all captured leakage volume flows, being supplied into onlyone of these two first gas volume flows. This will be discussed ingreater detail in connection with the figures. Alternatively, a separaterecirculation into two or more first gas volume flows is also possible.

The regenerative heat exchanger, according to an embodiment of theinvention, comprises a rotor having at least two gas volume flowsflowing through it, the rotor having a first front side, at which aninflowing first gas volume flow to be heated enters the rotor, and therotor also having a second front side, opposite to the first front side,at which the outflowing first gas volume flow to be heated exits fromthe rotor again. Furthermore, the rotor comprises at least one rotorseal, such as a radial seal and/or a peripheral seal in particular, forsealing the first and the second gas volume flows. The regenerative heatexchanger, according to an embodiment of the invention, additionallycomprises an acquisition unit or capture unit for a leakage volume flowwhich occurs in the area of a rotor seal, and at least one supply orsupply unit or recirculation unit, which is associated with thisacquisition unit or capture unit, for the acquired or captured leakagevolume flow into the first gas volume flow.

According to an embodiment of the invention, at least one capture unitis provided on the first front side of the rotor having at least oneassociated supply or supply unit for the leakage volume flow captured atthe first front side into the inflowing first gas volume flow, and/or atleast one capture unit is provided on the second front side having atleast one associated supply or supply unit for the leakage volume flowcaptured at the second front side into the outflowing first gas volumeflow.

The regenerative heat exchanger, according to an embodiment of theinvention, is preferably capable of using the method according to theinvention described above. The method features described above and theadvantages thereof are therefore transferable correspondingly to theregenerative heat exchanger according to an embodiment of the invention.

A capture unit is any unit which is capable of acquiring or capturing aleakage volume flow. A capture unit can be a system made of individualcomponents. A capture device is preferably a suction unit.

A supply or supply unit is used for supplying or recirculating a leakagevolume flow acquired or captured using a capture unit into the first gasvolume flow. A supply or a supply unit is preferably implemented by aline system, through which the leakage volume flow acquired or capturedon a rotor seal is supplied in a defined manner to the first gas volumeflow. If the leakage volume flow originates from the first gas volumeflow, the supply or supply unit is, strictly speaking, a recirculationor recirculation unit.

The line system of at least one supply or supply unit preferablycomprises at least one fan unit, using which a defined flow can begenerated in this line system.

The fan unit is designed so that a partial vacuum can be generated in aconnection line, which is situated between this fan unit and a rotorseal, using which the leakage volume flow can be suctioned at therelevant rotor seal. In particular, the rotor seal is at least oneradial seal and/or at least one peripheral seal which has a flowconnection to the fan unit via the connection line. At least one radialseal and/or at least one peripheral seal is preferably implemented asdivided and/or has multiple openings, so that a leakage volume flowoccurring at this rotor seal can be suctioned in a simplified manner.

The same fan unit also generates an overpressure in a connection linewhich is situated between this fan unit and the first gas volume flow,using which the leakage volume flow suctioned at the rotor seal can besupplied to the first gas volume flow and/or recirculated therein,strictly speaking, can be introduced or fed therein.

It is particularly preferably provided that at least one suction orsuction unit for a leakage volume flow is provided on the first frontside of the rotor, in particular in the area of a radial seal and/or aperipheral seal, having an associated supply or supply unit for thesuctioned leakage volume flow into the inflowing first gas volume flow.It is also provided that at least one suction unit for a leakage volumeflow is provided on the second front side of the rotor, in particular inthe area of a radial seal and/or a peripheral seal, having an associatedsupply or supply unit for the suctioned leakage volume flow into theoutflowing first gas volume flow. The supplies or supply units areimplemented separately from one another and each comprise at least onefan unit. This corresponds to a preferred and particularly advantageousexemplary embodiment of the invention.

The invention may also be implemented similarly on a heat exchangerhaving stationary heat-storing masses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a preferred exemplary embodiment of the invention in aschematic illustration.

FIG. 2 shows an alternative exemplary embodiment of the invention in aschematic illustration.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawingfigures, in which like reference numerals refer to like partsthroughout.

FIG. 1 shows a regenerative heat exchanger, identified as a whole by 1,which is used in a power plant. It comprises a circular-cylindricalrotor 2, which is horizontally oriented and is mounted so it isrotatable around the vertical axis 3. Heat stores 4 (such as heattransfer plate packs as described at the beginning) are located in theinterior of the rotor 2. The rotor has a first, lower front side 5 a, asecond, upper front side 5 b, and a lateral wall (peripheral wall)₇.Radial seals 8 a and 8 b (not specified in greater detail) andperipheral seals 9 a and 9 b (not specified in greater detail) arelocated on the front sides 5 a and 5 b.

According to the illustration, the rotor 2 has a first gas volume flow10, this being a fresh air volume flow, flowing through it from bottomto top on the left side. The fresh air volume flow 10 is suctioned by afan unit 14 and supplied to the rotor 2. The fresh air volume flow 10enters the rotor on the lower front side 5 a of the rotor 2 and exitsagain on the upper front side 5 b and is heated on the heat stores 4 asit flows through the rotor 2, which cool to the same extent in this case(as described at the beginning). In relation to the rotor 2, theinflowing fresh air volume flow is identified by 10 a and the outflowingfresh air volume flow by 10 b.

On the right side, the rotor 2 has a second gas volume flow 11, thisbeing a flue gas volume flow from a combustion process flowing throughit from top to bottom. The flue gas volume flow 11 enters the rotor 2 atthe upper front side 5 b and exits the rotor 2 again at the lower frontside 5 a and is cooled on the cool heat stores 4 as it flows through therotor 2, which heat up to the same extent in this case and aresubsequently available for heating the fresh air volume flow 10 (asdescribed at the beginning) After leaving the rotor 2, the alreadycooled flue gas volume flow is supplied to flue gas purificationfacilities and/or filter units 20.

As a result of the flow through in opposite directions, the temperaturesof both gas volume flows 10 and 11 are higher at the upper, second frontside 5 b of the rotor 2 than at the lower, first front side 5 a.Therefore, the upper front side 5 b can also be referred to as the “hotside” and the lower front side 5 a as the “cold side”.

In order to seal the two gas volume flows 10 and 11 on the rotor 2, theradial seals 8 a and 8 b and the peripheral seals 9 a and 9 b areprovided. The peripheral seals 9 a and 9 b are to seal the gas volumeflows 10 and 11 at the outer edge or outer circumference of the rotor 2,while the radial seals 8 a and 8 b are to prevent mixing of the gasvolume flows 10 and 11 by flow short-circuits and/or short-circuitvolume flows. As a result of alternating thermal and mechanical strain,there are always gaps or residual gaps between the seals 8 a, 8 b, 9 a,and 9 b and the rotor 2, through which leakage volume flows occur. Inparticular in the area of the radial seals 8 a and 8 b, leakage volumeflows are additionally favored by pressure differences in the gas volumeflows 10 and 11, the fresh air volume flow 10 usually having a higherpressure than the flue gas volume flow 11 because of the fan unit 14.This results in fresh air leakage volume flows 12 a and 12 b, so thatfresh air is transferred or flows into the flue gas volume flow 11 at alower temperature level, which results in an undesirable anddisadvantageous cooling effect in the flue gas volume flow 11 (asdescribed in greater detail above).

It is therefore provided that the leakage volume flows 12 a and 12 b arecaptured in the area of the radial seals 8 a and 8 b and the leakagevolume flows from the “hot” front side 5 b of the rotor 2 are to besupplied to the outflowing fresh air volume flow 10 b or introducedtherein and the leakage volume flows from the “cold” front side 5 a ofthe rotor 2 are to be supplied to the inflowing gas volume flow 10 a orintroduced therein. Through this separate recirculation of the leakagevolume flows from the “hot” front side into the already heatedoutflowing fresh air volume flow 10 b and from the “cold” side into thestill cool inflowing fresh air volume flow 10 a, the undesired anddisadvantageous cooling effect described above can be avoided in theflue gas volume flow 11, whereby the efficiency of the heat exchangerand thus also of the power plant can be increased as a result (asexplained in greater detail above). The condensation of critical fluegas components in cold temperature strands can also be prevented or atleast reduced in the flue gas to be cooled.

The capturing of the leakage volume flows and/or fresh air leakagevolume flows 12 a and 12 b is performed by suctioning at the radialseals 8 a and 8 b. In order to simplify the suctioning, the radial seals8 a and 8 b may be implemented as divided and/or having a plurality ofopenings (not shown), through which a partial vacuum may be effectivelyapplied in the gap or residual gap between the radial seal 8 a and 8 band the rotor 2 and the leakage volume flows may thus be captured. Thepartial vacuum is generated in each case by a fan unit 16 a and 16 b,which can be a ventilator or the like, for example. A connection line 17a or 17 b, via which the captured or suctioned leakage volume flows 12 aand 12 b are conducted away, is situated in each case between the fanunit 16 a and 16 b and the radial seals 8 a and 8 b. A connection line18 a or 18 b, respectively, extends from the fan unit 16 a and 16 b intothe inflowing fresh air volume flow 10 a or 10 b. These connection lines18 a and 18 b are used for supplying or recirculating the capturedleakage volume flows 12 a and 12 b, which were conducted away, into thefresh air volume flow 10. The fan units 16 a and 16 b are designed sothat they generate a partial vacuum in the connection lines 17 a and 17b and an overpressure in the connection lines 18 a and 18 b.

The connection lines 17 a and 18 a form, together with the fan unit 16 ahere, a line system for the supply or recirculation of a leakage volumeflow 12 a captured or suctioned at the first front side (“cold side”) 5a of the rotor 2 into the inflowing fresh air volume flow 10 a.Independently thereof, the connection lines 17 b and 18 b form, togetherwith the fan unit 16 b here, a second separate line system for thesupply or recirculation of a leakage volume flow 12 b captured orsuctioned at the second front side (“hot side”) 5 b of the rotor 2 intothe outflowing fresh air volume flow 10 b. The line cross sections andthe fan performance are dimensioned correspondingly. It is also possibleto segment the connection lines or to situate multiple connection linesin parallel. It is also possible to provide multiple fan units inparallel or in series.

Alternatively to the exemplary embodiment described above, it is alsopossible to provide suctioning and supply or recirculation at only oneof the front sides 5 a and 5 b of the rotor 2 (not shown), whereby asignificant improvement of the efficiency already results with lessconstruction effort. Alternatively or additionally, the leakage volumeflows may also be captured at the peripheral seals 9 a and 9 b andsupplied to the inflowing fresh air volume flow 10 a or the outflowingfresh air volume flow 10 b and fed or introduced therein. This is shownfor exemplary purposes on the left side of the rotor 2 in FIG. 1 using adashed line for the peripheral seal 9 a. A further fan unit can be usedfor the suctioning and supply or recirculation (in this case into theinflowing fresh air volume flow 10 a) or the fan unit 16 a can also beused for suctioning the leakage volume flow 12 a at the lower front side5 a. In order to also simplify the suctioning at the peripheral seals 9a and 9 b, the radial seals 8 a and 8 b may be implemented as dividedand/or having a plurality of openings. The efficiency of theregenerative heat exchanger 1 can be improved further by the suctioningof a leakage volume flow at least one of the peripheral seals 9 a and 9b. According to the invention, the supply or recirculation of a leakagevolume flow acquired at a peripheral seal 9 a at the lower front side(“cold side”) 5 a is performed into the inflowing, still cool fresh airvolume flow 10 a and the supply or recirculation of a leakage volumeflow acquired at a peripheral seal 9 b at the upper front side (“hotside”) 5 b is performed into the outflowing, heated fresh air volumeflow 10 b.

FIG. 2 shows an alternative exemplary embodiment of the invention. Onlythe differences from the exemplary embodiment of FIG. 1 (see abovestatements) are discussed hereafter. Therefore, the above statements onthe exemplary embodiment of FIG. 1 apply accordingly.

The essential difference from the exemplary embodiment of FIG. 1 is thatthe rotor 2 has two separate gas volume flows 100 and 101 flowingthrough it in the same direction on its left side, which are each heatedas they flow through the rotor. The gas volume flow 100 can be asecondary air volume flow, for example, and the gas volume 101 can be aprimary air volume flow, for example. These gas volume flows 100 and 101are used for different intended purposes in a power plant.Notwithstanding the illustration, in which the two gas volume flows 100and 101 flow through the rotor 2 adjacent to one another, they may alsoflow through the rotor at different points in relation to the rotorcross-section. The separate supply or recirculation of the leakagevolume flows captured or suctioned at the radial seals 8 a and 8 b isperformed here, on both sides of the rotor 2 according to the abovestatements, into the same gas volume flow 100 in each case (secondaryair volume flow). Alternatively, it is also possible to supply thecaptured leakage volume flows to the other gas volume flow 101 (primaryair volume flow).

It is also conceivable in the exemplary embodiment of FIG. 2 to providethe suctioning of a leakage volume flow at only one front side 5 a or 5b of the rotor 2. The suctioning of a leakage volume flow can also beperformed at a peripheral seal 9 a and/or 9 b, as described above.

The many features and advantages of the invention are apparent from thedetailed specification, and, thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, and,accordingly, all suitable modifications and equivalents may be resortedto that fall within the scope of the invention.

1. A method for operating a regenerative heat exchanger, including arotor having a first front side with a rotor seal and a second frontside with a rotor seal, through which a first gas volume flow is heatedand a second gas volume flow is cooled, the first gas volume flowflowing into the rotor at the first front side and flowing out of therotor at the second front side, the method comprising: capturing aleakage volume flow at the first front side of the rotor in the area ofthe rotor seal; supplying the leakage volume flow, captured at the firstfront side of the rotor, to the inflowing first gas volume flow;capturing a leakage volume flow at the second front side of the rotor inthe area of the rotor seal; and supplying the leakage volume flow,captured at the second front side of the rotor, to the outflowing firstgas volume flow.
 2. The method according to claim 1, wherein the leakagevolume flow captured at the first front side of the rotor is introducedinto the inflowing first gas volume flow upstream from the rotor, andthe leakage volume flow captured at the second front side of the rotoris introduced into the outflowing first gas volume flow downstream fromthe rotor.
 3. The method according to claim 2, wherein the leakagevolume flows are introduced into the first gas volume flow proximate tothe rotor.
 4. The method according to claim 1, wherein the leakagevolume flows, captured at the first front side of the rotor and at thesecond front side of the rotor, are separately supplied to the inflowingfirst gas volume flow and the outflowing first gas volume flow,respectively.
 5. The method according to claim 4, wherein theregenerative heat exchanger includes respective fan units to capture theleakage volume flows from the rotor and supply the leakage volume flowsto the first gas volume flow.
 6. The method according to claim 1,wherein the rotor seals are radial seals, said capturing a leakagevolume flow at the first front side of the rotor in the area of therotor seal is performed by suctioning, and said capturing a leakagevolume flow at the second front side of the rotor in the area of therotor seal is performed by suctioning.
 7. The method according to claim1, wherein the rotor seals are peripheral seals, said capturing aleakage volume flow at the first front side of the rotor in the area ofthe rotor seal is performed by suctioning, and said capturing a leakagevolume flow at the second front side of the rotor in the area of therotor seal is performed by suctioning.
 8. The method according to claim1, wherein the first gas volume flow and the second gas volume flow passthrough the rotor in opposite directions.
 9. The method according toclaim 1, wherein an additional gas volume flow flows through the rotorand is not supplied with leakage volume flows.
 10. A regenerative heatexchanger, comprising: a rotor, having a first front side with a rotorseal and a second front side with a rotor seal, through which a firstgas volume flow is heated and a second gas volume flow is cooled, thefirst gas volume flow flowing into the rotor at the first front side andflowing out of the rotor at the second front side; a first unit forcapturing a leakage volume flow at the first front side of the rotor inthe area of the rotor seal and supplying the leakage volume flow to theinflowing first gas volume flow; and a second unit for capturing aleakage volume flow at the second front side of the rotor in the area ofthe rotor seal for supplying the leakage volume flow to the outflowingfirst gas volume flow.
 11. The regenerative heat exchanger according toclaim 10, wherein the first unit is connected to the rotor and theinflowing first gas volume flow through a first line system, and thesecond unit is connected to the rotor and the outflowing first gasvolume flow through a second line system.
 12. The regenerative heatexchanger according to claim 11, wherein the first and second units arefans.
 13. The regenerative heat exchanger according to claim 10, whereinthe rotor seals are radial seals or peripheral seals.
 14. Theregenerative heat exchanger according to claim 10, wherein the rotorseals are divided or provided with multiple openings.
 15. Theregenerative heat exchanger according to claim 10, wherein the first andsecond units are suction units.
 16. A regenerative heat exchanger,comprising: a rotor, including a lower side with a rotor seal, an upperside with a rotor seal and a heat storing mass disposed therebetween,through which a gas volume flow is heated; a fan unit for capturing aleakage volume flow at the lower side of the rotor in the area of therotor seal and supplying the leakage volume flow to the gas volume flowbefore the gas volume flow enters the rotor.
 17. The regenerative heatexchanger according to claim 16, further comprising an additional fanunit for capturing a leakage volume flow at the upper side of the rotorin the area of the rotor seal and supplying the leakage volume flow tothe gas volume flow after the gas volume flow exits the rotor.
 18. Theregenerative heat exchanger according to claim 16, wherein the rotorseal is a radial seal.
 19. The regenerative heat exchanger according toclaim 16, wherein the rotor seal is a peripheral seal.
 20. Theregenerative heat exchanger according to claim 16, wherein each rotorseal includes a plurality of openings.